Truncatella (gastropod)

Truncatella
Two live individuals of Truncatella subcylindrica: a juvenile on the left, and an adult on the right
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
(unranked):	clade Caenogastropoda clade Hypsogastropoda clade Littorinimorpha
Superfamily:	Rissooidea
Family:	Truncatellidae
Subfamily:	Truncatellinae
Genus:	Truncatella Risso, 1826[1]

Truncatella is a genus of very small land snails with an operculum, terrestrial gastropod mollusks in the family Truncatellidae. These small and minute snails live on land, very close to seawater. They walk with a strange looping action, and the adults have truncated shells. Many of the species are small enough to be considered micromollusks.

Truncatella is the type genus of the family Truncatellidae.^[2]

Distribution and habitat

This genus occurs in tropical and subtropical areas. The various species of Truncatella are pantropical in distribution, with a few exceptions such as Truncatella truncatula and Truncatella subcylindrica.

Most of the species in this genus live in a habitat that is neither fully terrestrial nor fully marine: they live under plant debris near high tide level, where they are occasionally wetted with seawater by waves. A small minority of the species are fully terrestrial.

These small snails are typically found associated with drifts of plant material, where their eggs are deposited.^[3]

The adaptations of these land snails to the terrestrial environment are not so perfect as they are in the more usual pulmonate land snails, and their terrestrial adaptations may in fact be comparatively recent.^[4]

Species

Shells of Truncatella scalarina

Shells of Truncatella vincentiana

The genus Truncatella was erected by Antoine Risso (Risso, 1826)^[1] for T. costulata (now T. subcylindrica), which is the type species for this genus.

There are several genera within the Truncatellidae, but the eponymous genus Truncatella is the largest (in terms of number of species); other genera in the family are Geomelania, Taheitia, and Blandiella.^[5][6][7]

There are approximately 30 species in the genus Truncatella, including:

• Truncatella avenacea Garrett, 1887^[8]
• Truncatella bahamensis Pfeiffer, 1856
• Truncatella bairdiana C. B. Adams, 1852^[9]
• Truncatella brazieri Cox, 1868^[10]
• Truncatella californica Pfeiffer, 1857^[11] - California truncatella
• Truncatella caribaeensis Reeve, 1842^[12] - Caribbean truncatella
• Truncatella ceylanica Pfeiffer, 1857^[13]
• Truncatella clathrus Lowe, 1832^[14]
• Truncatella diaphana Gassies, 1869^[15]
• Truncatella ferruginea (Cox, 1868)^[16]
• Truncatella granum Garrett, 1872^[17]
• Truncatella guerinii Villa & Villa, 1841^[18]
• Truncatella kiusiuensis Pilsbry, 1902^[19]
• Truncatella marginata Küster, 1855^[20]
• Truncatella obscura Morelet, 1882^[21]
• Truncatella pellucida Dohrn, 1860^[22]
• Truncatella pfeifferi Martens, 1860^[16]
• Truncatella pulchella Pfeiffer, 1839^[23][24] - beautiful truncatella - synonyms: Truncatella bilabiata, Truncatella bilabiata bilabiata, Truncatella bilabiata barbadensis.^[25]
• Truncatella quadrasi Möllendorff, 1893^[26]
• Truncatella rostrata Gould, 1848^[27]
• Truncatella rustica Mousson, 1865^[28]
• Truncatella scalarina Cox, 1867^[29]
• Truncatella scalaris (Michaud, 1830)^[30] - ladder truncatella
• Truncatella stimpsonii Stearns, 1872^[31]
• Truncatella subcylindrica (Linnaeus, 1767)^[32]
• Truncatella teres (Pfeiffer, 1857)^[16]
• Truncatella thaanumi Clench & Turner, 1948^[33]
• Truncatella truncatula
• Truncatella vincentiana Cotton, 1942^[16]
• Truncatella yorkensis (Cox, 1868)^[16]

Description

From left: Truncatella bahamensis (holotype), T. bilabiata bilabiata, T. pulchella.^[5]

As implied by the name, these snails are notable for the way they modify their elongated shells as they mature, breaking off several of the apical whorls, and forming a relatively smooth seal for the remainder of the shell.

Locomotion

The method of locomotion used by Truncatella is unusual.^[34] Instead of gliding over a slime trail using minute waves in its foot, Truncatella uses a very large and muscular proboscis to reach ahead and grasp a surface, at which point the small foot releases its hold and the proboscis contracts to pull the animal forward, after which the entire procedure is usually repeated.^[35]

References

External links

Wikimedia Commons has media related to Truncatella.

• Truncatella at the National Center for Biotechnology Information
• "Genus summary for Truncatella" AnimalBase.